Some public-address system include high-impedance connection of a power amplifier to a plurality of loudspeakers, as disclosed in Non-patent Literature 1. In high-impedance connection, a voice coil of each loudspeaker is connected in a secondary side of a matching transformer. The impedance of the secondary side is made to match with the impedance of the voice coil. The impedance of the primary side of the matching transformer is chosen to be high. The primary sides of these matching transformers are connected in parallel via a set of transmission lines, and, then, connected to the output of the power amplifier. The output impedance of the power amplifier is made to mach with the parallel impedance of the parallelly connected matching transformers, and the power amplifier is adapted to provide a high output voltage. With this arrangement, loss in the transmission lines can be reduced.    Non-Patent Literature 1: Revised New Edition of PA Audio System edited by Shigeo Fujioka, published by Kogaku Tosho Shuppan K K, Page 200